Nanotubes are commonly made from carbon and comprise graphite sheets seamlessly wrapped into cylinders. Nanotubes can be single-walled or multi-walled. Single-walled nanotubes (SWNTs) comprise single cylinders and represent nearly ideal one dimensional electronic structures. Multi-walled nanotubes (MWNTs) comprise multiple cylinders arranged concentrically. Typical dimensions are 1-3 nm for SWNTs and 20-100 nm for MWNTs.
Nanotubes can be either metallic or semiconducting depending on their structure. Traditional nanotubes are contaminated by metallic catalyst, which serve as root of grown nanotubes.
Traditional nanotubes are contaminated by metallic catalyst, which serve as root of grown nanotubes. Additional processes are needed to purify the as grown CNTs. This is a slow process and requires special training. Currently, researchers are focused on the slow, post-growth purification process.
In addition, another challenge facing nanotube synthesis today is that all methods result in a heterogeneous mixture of different nanotube diameters and chiralities. More specifically, all known synthesis methods results in a mixture of (n,m) indices, where (n,m) describes the crystal structure of the nanotubes. Both semiconducting and metallic nanotubes are present in the mixture. Of the semiconducting nanotubes, different diameters lead to different band gaps, affecting the electronic properties.
Thus, it is desirable to provide a method of nanotube systhesis that results in a homogeneous mixture of nanotubes having the same diameters and chiralities, and avoids the slowness and the impurities or defects that are usually encountered with the process for as-grown carbon nanotubes.